The movement in this game is weird to get used to and the double jump mechanic itself is inconsistent and nonintuitive. It was only near the turtle guardian route that I figured out the double jump has to be executed a specific way, which isn't the case in other games with double jumps. To explain, you can't just spam the jump key to execute a double jump and the double jump itself isn't on a cooldown. Rather you have to press the second jump a moment after the first jump, almost like a combo in a fighting game, but even more inconsistent than a true combo as a 2012er from the FGC. The movement physics are strange in and of itself with the regular single jumps falling down abruptly reminiscent of old adventure platformers on DOS, so I cannot fault it that much even though that is a dated mechanic.
And as a fan of difficult platformers like The End is Nigh, which feels smoother, more responsive, and fair, I wasn't a fan of this game at all. The jump mechanics are atrocious, but the level design makes it far worse. The addition of ghouls that pop out, not only ruin the pacing of the game, but detract from any semblance of momentum when on a good run. The decision to make the enemies into bullet sponges is alright and make sense for those enemies that shoot projectiles, but for enemies like zombies and ghouls that stand still and even the frogs which mostly stand still and jump occasionally serve merely as roadblocks that take time rather than being a fun way to kill an enemy. The bosses themselves are for the most part good, but the buggy nature of the game where some bosses don't let you exit the screen and thus negates any difficulty in beating them as you respawn constantly while their health does not regenerate (unless as said you do leave the screen and come back). Most of the bosses allow this, but there are 1-2 bosses that make this impossible as the doors are shut locked. I didn't find any issue with hitboxes at all nor did I find the spider boss to be problematic. The baiting of bosses and dodging were on point, and I found the spider boss the most enjoyable, having left the screen if I died once to make things more fun for myself. Leaving the screen, resets the game screen with enemies as long as you don't defeat the boss.
The monochrome art style hurts the gameplay even more as you not only deal with ghouls that come out of the ground but you also deal with spikes that are white. This is also compounded with the fact that spikes on the ceilings that don't hurt you look very similar to dangerous spikes and they are all white as well.
The addition of checks to prevent the player from skipping a boss is still buggy. I managed to skip the wizard who says you cannot leave unless you met 5 guardians. I don't know how I managed, but I was pressing the interact key and the shoot key and managed to exit the conversation and enter the doorway past him. I did read that you should experience most of the content from the discussions here so I just exited out the doorway and found the final guardian before returning and playing it as intended.
I'm a fan of 2d platformers, even those with weird movement mechanics like Gish, but this game really didn't mesh with me. There is definitely a good game inside here, but with all its failings, I would not recommend this game at all.